Android tutorial: How to parse / read JSON data into a Android ListView

06.08.2011

 | 73201 views | 

inShare3

Today we get on with our series that will connect our Android applications to internet webservices!

Next up in line: from JSON to a Listview. A lot of this project is identical to the previous post in this series so try to look there first if you have any problems. On the bottom of the post ill add the Eclipse project with the source.

For this example i made use of an already existing JSON webservice located here.

This is a piece of the JSON array that gets returned:

view source

print?

01.{"earthquakes": [

02.{

03."eqid": "c0001xgp",

04."magnitude": 8.8,

05."lng": 142.369,

06."src": "us",

07."datetime": "2011-03-11 04:46:23",

08."depth": 24.4,

09."lat": 38.322

10.},

11.{

12."eqid": "2007hear",

13."magnitude": 8.4,

14."lng": 101.3815,

15."src": "us",

16."datetime": "2007-09-12 09:10:26",

17."depth": 30,

18."lat": -4.5172

19.}

20.<--more -->

21. 

22.]}

So how do we get this data into our application! Behold our getJSON class!

getJSON(String url)

view source

print?

01.public static JSONObject getJSONfromURL(String url){

02. 

03.//initialize

04.InputStream is = null;

05.String result = "";

06.JSONObject jArray = null;

07. 

08.//http post

09.try{

10.HttpClient httpclient = new DefaultHttpClient();

11.HttpPost httppost = new HttpPost(url);

12.HttpResponse response = httpclient.execute(httppost);

13.HttpEntity entity = response.getEntity();

14.is = entity.getContent();

15. 

16.}catch(Exception e){

17.Log.e("log_tag", "Error in http connection "+e.toString());

18.}

19. 

20.//convert response to string

21.try{

22.BufferedReader reader = new BufferedReader(newInputStreamReader(is,"iso-8859-1"),8);

23.StringBuilder sb = new StringBuilder();

24.String line = null;

25.while ((line = reader.readLine()) != null) {

26.sb.append(line + "\n");

27.}

28.is.close();

29.result=sb.toString();

30.}catch(Exception e){

31.Log.e("log_tag", "Error converting result "+e.toString());

32.}

33. 

34.//try parse the string to a JSON object

35.try{

36.jArray = new JSONObject(result);

37.}catch(JSONException e){

38.Log.e("log_tag", "Error parsing data "+e.toString());

39.}

40. 

41.return jArray;

42.}

The code above can be divided in 3 parts.

1. the first part makes the HTTP call
2. the second part converts the stream into a String
3. the third part converts the string to a JSPNObject

Now we only have to implement this into out ListView. We can use the same method as in the XML tutorial. We make a HashMap that stores our data and we put JSON values in the HashMap. After that we will bind that HashMap to a SimpleAdapter. Here is how its done:

Implementation

view source

print?

01.ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

02. 

03.//Get the data (see above)

04.JSONObject json =

05.JSONfunctions.getJSONfromURL("http://api.geonames.org/postalCodeSearchJSON?formatted=true&;postalcode=9791&maxRows=10&username=demo&style=full");

06. 

07.try{

08.//Get the element that holds the earthquakes ( JSONArray )

09.JSONArray  earthquakes = json.getJSONArray("earthquakes");

10. 

11.//Loop the Array

12.for(int i=0;i < earthquakes.length();i++){                      

13. 

14.HashMap<String, String> map = new HashMap<String, String>();

15.JSONObject e = earthquakes.getJSONObject(i);

16. 

17.map.put("id",  String.valueOf(i));

18.map.put("name", "Earthquake name:" + e.getString("eqid"));

19.map.put("magnitude", "Magnitude: " +  e.getString("magnitude"));

20.mylist.add(map);

21.}

22.}catch(JSONException e)        {

23.Log.e("log_tag", "Error parsing data "+e.toString());

24.}

 After this we only need to make up the Simple Adapter

view source

print?

01.ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.main,

02.new String[] { "name", "magnitude" },

03.new int[] { R.id.item_title, R.id.item_subtitle });

04. 

05.setListAdapter(adapter);

06. 

07.final ListView lv = getListView();

08.lv.setTextFilterEnabled(true);

09.lv.setOnItemClickListener(new OnItemClickListener() {

10.public void onItemClick(AdapterView<?> parent, View view, intposition, long id) {

11.@SuppressWarnings("unchecked")

12. 

13.Toast.makeText(Main.this, "ID '" + o.get("id") + "' was clicked.", Toast.LENGTH_SHORT).show();

14. 

15.}

16.});

Now we have a ListView filled with JSON data!